package com.easycoding.framework.util;

import java.lang.reflect.Array;

/**
 * <b>Descript</b>:MD5算法的Java Bean实现以及使用示范<br>
 * MD5类实现了RSA Data Security, Inc.在提交给IETF的RFC1321中的MD5 message-digest算法。<br/>
 * <b>Create Date</b>: 2007-10-25<br/>
 * <b>Version</b>: Since JDK 1.5.0<br/>
 * <b>Package</b>: com.easycoding.framework.util
 */
public class MD5
{
	/*
     * 下面这些S11-S44实际上是一个4*4的矩阵，在原始的C实现中是用#define 实现的，
	 *这里把它们实现成为static final是表示了只读，切能在同一个进程空间内的多个
	 *Instance间共享
     */
    static final int S11 = 7;
    static final int S12 = 12;
    static final int S13 = 17;
    static final int S14 = 22;

    static final int S21 = 5;
    static final int S22 = 9;
    static final int S23 = 14;
    static final int S24 = 20;

    static final int S31 = 4;
    static final int S32 = 11;
    static final int S33 = 16;
    static final int S34 = 23;

    static final int S41 = 6;
    static final int S42 = 10;
    static final int S43 = 15;
    static final int S44 = 21;
    
    static final byte[] PADDING = { -128, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
    /*
     * 下面的三个成员是MD5计算过程中用到的3个核心数据，在原始的C实现中
     * 被定义到MD5_CTX结构中
     */
    private long[] state = new long[4];//state (ABCD)
    private long[] count = new long[2];//number of bits, modulo 2^64 (lsb first)
    private byte[] buffer = new byte[64]; //input buffer
    
    /*
     * digestHexStr是MD5的唯一一个公共成员，是最新一次计算结果的
	 * 16进制ASCII表示.
     */
    public String digestHexStr;
    
    /*
     * digest,是最新一次计算结果的2进制内部表示，表示128bit的MD5值.
     */
    private byte[] digest = new byte[16];
    
    /**
     * MD5这个类的标准构造函数，JavaBean要求有一个public的并且没有参数的构造函数
     */
    public MD5()
    {
        md5Init();
        return;
    }
    
    /**
     * 类MD5最主要的公共方法，入口参数是你想要进行MD5变换的字符串
	 * 返回的是变换完的结果，这个结果是从公共成员digestHexStr取得的．
     * @param inbuf 进行MD5变换的字符串
     * @return 进行MD5变换后的字符串
     */
    public String getMD5Hash(String inbuf) 
    {
        if(inbuf == null)
        	return null;
    	md5Init();
        md5Update(inbuf.getBytes(), inbuf.length());
        md5Final();
        digestHexStr = "";
        for (int i = 0; i < 16; i++) 
        {
                digestHexStr += byteHEX(digest[i]);
        }
        return digestHexStr;
    }
    
    /**
     * 初始化函数，初始化核心变量，装入标准的幻数
     */
    private void md5Init() 
    {
        count[0] = 0L;
        count[1] = 0L;
        //Load magic initialization constants.
        state[0] = 0x67452301L;
        state[1] = 0xefcdab89L;
        state[2] = 0x98badcfeL;
        state[3] = 0x10325476L;
        return;
    }
    
    /*
     * F, G, H ,I 是4个基本的MD5函数，在原始的MD5的C实现中，由于它们是
     * 简单的位运算，可能出于效率的考虑把它们实现成了宏，在java中，我们把它们
     * 实现成了private方法，名字保持了原来C中的。
     */
    private long F(long x, long y, long z) 
    {
        return (x & y) | ((~x) & z);
    }
    private long G(long x, long y, long z) 
    {
        return (x & z) | (y & (~z));
    }
    private long H(long x, long y, long z) 
    {
        return x ^ y ^ z;
    }
    private long I(long x, long y, long z) 
    {
        return y ^ (x | (~z));
    }

    private long FF(long a, long b, long c, long d, long x, long s,
            long ac) {
            a += F (b, c, d) + x + ac;
            a = ((int) a << s) | ((int) a >>> (32 - s));
            a += b;
            return a;
    }

    /*
     * FF,GG,HH和II将调用F,G,H,I进行近一步变换
     * FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
     * Rotation is separate from addition to prevent recomputation.
     */
    private long GG(long a, long b, long c, long d, long x, long s,long ac) 
    {
            a += G (b, c, d) + x + ac;
            a = ((int) a << s) | ((int) a >>> (32 - s));
            a += b;
            return a;
    }
    private long HH(long a, long b, long c, long d, long x, long s,long ac) 
    {
            a += H (b, c, d) + x + ac;
            a = ((int) a << s) | ((int) a >>> (32 - s));
            a += b;
            return a;
    }
    private long II(long a, long b, long c, long d, long x, long s,long ac) 
    {
            a += I (b, c, d) + x + ac;
            a = ((int) a << s) | ((int) a >>> (32 - s));
            a += b;
            return a;
    }
    
    /**
     * MD5的主计算过程，inbuf是要变换的字节串，inputlen是长度，这个
     * 函数由getMD5ofStr调用，调用之前需要调用md5init
     * @param inbuf 要变换的字节串
     * @param inputLen 长度
     */
    private void md5Update(byte[] inbuf, int inputLen) 
    {
        int i, index, partLen;
        byte[] block = new byte[64];
        index = (int)(count[0] >>> 3) & 0x3F;
        //Update number of bits
        if((count[0] += (inputLen << 3)) < (inputLen << 3))
            count[1]++;
        count[1] += (inputLen >>> 29);
        partLen = 64 - index;
        //Transform as many times as possible.
        if(inputLen >= partLen) 
        {
            md5Memcpy(buffer, inbuf, index, 0, partLen);
            md5Transform(buffer);
            for(i = partLen; i + 63 < inputLen; i += 64) 
            {
                md5Memcpy(block, inbuf, 0, i, 64);
                md5Transform (block);
            }
            index = 0;            
        } 
        else
            i = 0;
        /* Buffer remaining input */
        md5Memcpy(buffer, inbuf, index, i, inputLen - i);
    }
    
    /**
     * 整理和填写输出结果
     */
    private void md5Final () 
    {
        byte[] bits = new byte[8];
        int index, padLen;
        ///* Save number of bits */
        Encode (bits, count, 8);
        ///* Pad out to 56 mod 64.
        index = (int)(count[0] >>> 3) & 0x3f;
        padLen = (index < 56) ? (56 - index) : (120 - index);
        md5Update (PADDING, padLen);
        ///* Append length (before padding) */
        md5Update(bits, 8);
        ///* Store state in digest */
        Encode (digest, state, 16);
    }
    
    /**
     * 内部使用的byte数组的块拷贝函数，从input的inpos开始把len长度的
　　　* 字节拷贝到output的outpos位置开始
     * @param output
     * @param input
     * @param outpos
     * @param inpos
     * @param len
     */
    private void md5Memcpy(byte[] output,byte[] input,int outpos,int inpos,
            int len)
    {
        int i;
        for(i = 0; i < len; i++)
            output[outpos + i] = input[inpos + i];
    }
    
    /**
     * MD5核心变换程序，有md5Update调用，block是分块的原始字节
     * @param block 分块的原始字节
     */
    private void md5Transform (byte block[]) 
    {
        long a = state[0], b = state[1], c = state[2], d = state[3];
        long[] x = new long[16];
        Decode (x, block, 64);
        /* Round 1 */
        a = FF (a, b, c, d, x[0], S11, 0xd76aa478L); /* 1 */
        d = FF (d, a, b, c, x[1], S12, 0xe8c7b756L); /* 2 */
        c = FF (c, d, a, b, x[2], S13, 0x242070dbL); /* 3 */
        b = FF (b, c, d, a, x[3], S14, 0xc1bdceeeL); /* 4 */
        a = FF (a, b, c, d, x[4], S11, 0xf57c0fafL); /* 5 */
        d = FF (d, a, b, c, x[5], S12, 0x4787c62aL); /* 6 */
        c = FF (c, d, a, b, x[6], S13, 0xa8304613L); /* 7 */
        b = FF (b, c, d, a, x[7], S14, 0xfd469501L); /* 8 */
        a = FF (a, b, c, d, x[8], S11, 0x698098d8L); /* 9 */
        d = FF (d, a, b, c, x[9], S12, 0x8b44f7afL); /* 10 */
        c = FF (c, d, a, b, x[10], S13, 0xffff5bb1L); /* 11 */
        b = FF (b, c, d, a, x[11], S14, 0x895cd7beL); /* 12 */
        a = FF (a, b, c, d, x[12], S11, 0x6b901122L); /* 13 */
        d = FF (d, a, b, c, x[13], S12, 0xfd987193L); /* 14 */
        c = FF (c, d, a, b, x[14], S13, 0xa679438eL); /* 15 */
        b = FF (b, c, d, a, x[15], S14, 0x49b40821L); /* 16 */

        /* Round 2 */
        a = GG (a, b, c, d, x[1], S21, 0xf61e2562L); /* 17 */
        d = GG (d, a, b, c, x[6], S22, 0xc040b340L); /* 18 */
        c = GG (c, d, a, b, x[11], S23, 0x265e5a51L); /* 19 */
        b = GG (b, c, d, a, x[0], S24, 0xe9b6c7aaL); /* 20 */
        a = GG (a, b, c, d, x[5], S21, 0xd62f105dL); /* 21 */
        d = GG (d, a, b, c, x[10], S22, 0x2441453L); /* 22 */
        c = GG (c, d, a, b, x[15], S23, 0xd8a1e681L); /* 23 */
        b = GG (b, c, d, a, x[4], S24, 0xe7d3fbc8L); /* 24 */
        a = GG (a, b, c, d, x[9], S21, 0x21e1cde6L); /* 25 */
        d = GG (d, a, b, c, x[14], S22, 0xc33707d6L); /* 26 */
        c = GG (c, d, a, b, x[3], S23, 0xf4d50d87L); /* 27 */
        b = GG (b, c, d, a, x[8], S24, 0x455a14edL); /* 28 */
        a = GG (a, b, c, d, x[13], S21, 0xa9e3e905L); /* 29 */
        d = GG (d, a, b, c, x[2], S22, 0xfcefa3f8L); /* 30 */
        c = GG (c, d, a, b, x[7], S23, 0x676f02d9L); /* 31 */
        b = GG (b, c, d, a, x[12], S24, 0x8d2a4c8aL); /* 32 */

        /* Round 3 */
        a = HH (a, b, c, d, x[5], S31, 0xfffa3942L); /* 33 */
        d = HH (d, a, b, c, x[8], S32, 0x8771f681L); /* 34 */
        c = HH (c, d, a, b, x[11], S33, 0x6d9d6122L); /* 35 */
        b = HH (b, c, d, a, x[14], S34, 0xfde5380cL); /* 36 */
        a = HH (a, b, c, d, x[1], S31, 0xa4beea44L); /* 37 */
        d = HH (d, a, b, c, x[4], S32, 0x4bdecfa9L); /* 38 */
        c = HH (c, d, a, b, x[7], S33, 0xf6bb4b60L); /* 39 */
        b = HH (b, c, d, a, x[10], S34, 0xbebfbc70L); /* 40 */
        a = HH (a, b, c, d, x[13], S31, 0x289b7ec6L); /* 41 */
        d = HH (d, a, b, c, x[0], S32, 0xeaa127faL); /* 42 */
        c = HH (c, d, a, b, x[3], S33, 0xd4ef3085L); /* 43 */
        b = HH (b, c, d, a, x[6], S34, 0x4881d05L); /* 44 */
        a = HH (a, b, c, d, x[9], S31, 0xd9d4d039L); /* 45 */
        d = HH (d, a, b, c, x[12], S32, 0xe6db99e5L); /* 46 */
        c = HH (c, d, a, b, x[15], S33, 0x1fa27cf8L); /* 47 */
        b = HH (b, c, d, a, x[2], S34, 0xc4ac5665L); /* 48 */

        /* Round 4 */
        a = II (a, b, c, d, x[0], S41, 0xf4292244L); /* 49 */
        d = II (d, a, b, c, x[7], S42, 0x432aff97L); /* 50 */
        c = II (c, d, a, b, x[14], S43, 0xab9423a7L); /* 51 */
        b = II (b, c, d, a, x[5], S44, 0xfc93a039L); /* 52 */
        a = II (a, b, c, d, x[12], S41, 0x655b59c3L); /* 53 */
        d = II (d, a, b, c, x[3], S42, 0x8f0ccc92L); /* 54 */
        c = II (c, d, a, b, x[10], S43, 0xffeff47dL); /* 55 */
        b = II (b, c, d, a, x[1], S44, 0x85845dd1L); /* 56 */
        a = II (a, b, c, d, x[8], S41, 0x6fa87e4fL); /* 57 */
        d = II (d, a, b, c, x[15], S42, 0xfe2ce6e0L); /* 58 */
        c = II (c, d, a, b, x[6], S43, 0xa3014314L); /* 59 */
        b = II (b, c, d, a, x[13], S44, 0x4e0811a1L); /* 60 */
        a = II (a, b, c, d, x[4], S41, 0xf7537e82L); /* 61 */
        d = II (d, a, b, c, x[11], S42, 0xbd3af235L); /* 62 */
        c = II (c, d, a, b, x[2], S43, 0x2ad7d2bbL); /* 63 */
        b = II (b, c, d, a, x[9], S44, 0xeb86d391L); /* 64 */

        state[0] += a;
        state[1] += b;
        state[2] += c;
        state[3] += d;
    }
    
    /**
     * 把long数组按顺序拆成byte数组，因为java的long类型是64bit的，
     * 只拆低32bit，以适应原始C实现的用途
     * @param output
     * @param input
     * @param len
     */
    private void Encode (byte[] output, long[] input, int len)
    {
        int i, j;
        for (i = 0, j = 0; j < len; i++, j += 4) 
        {
            output[j] = (byte)(input[i] & 0xffL);
            output[j + 1] = (byte)((input[i] >>> 8) & 0xffL);
            output[j + 2] = (byte)((input[i] >>> 16) & 0xffL);
            output[j + 3] = (byte)((input[i] >>> 24) & 0xffL);
        }
    }
    
    /**
     * 把byte数组按顺序合成成long数组，因为java的long类型是64bit的，
     * 只合成低32bit，高32bit清零，以适应原始C实现的用途
     * @param output
     * @param input
     * @param len
     */
    private void Decode (long[] output, byte[] input, int len) 
    {
        int i, j;
        for(i = 0, j = 0; j < len; i++, j += 4)
            output[i] = b2iu(input[j])|(b2iu(input[j + 1]) << 8)|
            	(b2iu(input[j + 2]) << 16)|(b2iu(input[j + 3]) << 24);
        return;
    }
    
    /**
     * 把byte按照不考虑正负号的原则的＂升位＂程序，因为java没有unsigned运算
     * @param b
     * @return
     */
    public static long b2iu(byte b) 
    {
        return b < 0 ? b & 0x7F + 128 : b;
    }
    
    /**
     * 用来把一个byte类型的数转换成十六进制的ASCII表示，
	 * 因为java中的byte的toString无法实现这一点，我们又没有C语言中的
	 * sprintf(outbuf,"%02X",ib)
     * @param ib
     * @return
     */
    public static String byteHEX(byte ib) 
    {
        char[] Digit = { '0','1','2','3','4','5','6','7','8','9',
        'A','B','C','D','E','F' };
        char [] ob = new char[2];
        ob[0] = Digit[(ib >>> 4) & 0X0F];
        ob[1] = Digit[ib & 0X0F];
        String s = new String(ob);
        return s;
    }
    
    
    //本javabean的使用示范
    public static void main(String[] args)
    {
        MD5 m = new MD5();
        //如果没有参数，执行标准的Test Suite
        if(Array.getLength(args) == 0)
        {
            System.out.println("MD5 Test suite:");
            System.out.println("MD5(\"\"):"+"\n    "+m.getMD5Hash(""));
            System.out.println("MD5(\"a\"):"+"\n    "+m.getMD5Hash("a"));
        	System.out.println("MD5(\"abc\"):"+"\n    "+m.getMD5Hash("abc"));
        	System.out.println("MD5(\"message digest\"):"+"\n    "+
        	    m.getMD5Hash("message digest"));
        	System.out.println("MD5(\"abcdefghijklmnopqrstuvwxyz\"):"+"\n    "+
                m.getMD5Hash("abcdefghijklmnopqrstuvwxyz"));
        	System.out.println("MD5(\"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklm"+
        	    "nopqrstuvwxyz0123456789\"):"+"\n    "+m.getMD5Hash("ABCDEF"+
        	    "GHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"));
        }
        else
        {
            System.out.println("MD5(" + args[0] + ")=" + m.getMD5Hash(args[0]));
        }  
        /*
         * (new MD5()).getMD5Str("abc")
         * 效果同Param.getHexString(Param.getMD5Digest("abc"))
         */
    }
}
